Could be the same person:

https://hkmdb.com/db/people/view.mhtml? ... ay_set=eng

https://hkmdb.com/db/people/view.mhtml? ... ay_set=eng

https://hkmdb.com/db/people/view.mhtml? ... ay_set=eng

Additional information from another fan/expert:

1.1) Hou Hsia-San (侯小三)
In a portrait gallery from the movie credited for Hou Hsia-San
- "When Hell Broke Loose" (1975), there's a portrait of Ai Chi-San, but Ai Chi-San's name is not in the credits.
I was able to find articles about 2 TV-series starring Hou Hsia-San. The article for the first TV-series includes image of a guy,
who looks like Ai Chi-San:

https://kgbz.pixnet.net/blog/post/323205375

For the other TV-series I found 2 articles: in the first article they mention Hou Hsia-San (侯小三) who appears in that TV-series,
and in the other article there's a photo of Ai Chi-San, saying that this is Ai Chi-San (矮仔三). But I see this quite often that
in different articles for the same movie/TV-series the same actors are credited by their different names.
Here they are:

http://blog.sina.com.cn/s/blog_13fd8d4b30102yzbf.html
http://blog.sina.com.cn/s/blog_13fd8d4b30102yzbg.html

1.2) Hou Yuan-San (侯元三)
In a portrait gallery from the movie credited for Hou Yuan-San - "Shaolin Kung Fu" (1974), there's a portrait of Ai Chi-San,
but Ai Chi-San's name is not in the credits.

At the same time, on the poster of this movie there's Ai Chi-San's name, but no Hou Yuan-San's name.
Another movie credited for Hou Yuan-San in HKMDB is "Fixed Prize" (1969) - he has the 2nd billed role there.
Here I found kind of poster for that movie with more detailed cast:

https://tfi.openmuseum.tw/muse/digi_obj ... fc04c92f39

The 2nd billed actor's name there is Ai Chi-San, and no Hou Yuan-San's name.
In both cases every source lists only one of the names: or Hou Yuan-San or Ai Chi-San - that makes me think that they are indeed the same person.

1.3) Ai Chi-San's name - 矮仔三 - actually means “Shortie San” or "3rd Shortie" (maybe it's more correct to split it as Ai-Chi San?),
so it's not a real name, and if two other guys you mentioned - 侯元三 (Hou Yuan-San) and 侯小三 (Hou Hsia-San)(these two names seems to be proper Chinese names)
- also have the character 三 as part of the given name - this is an additional indicator, that it might be the same person.

Merged:

矮仔三 ♂
Ai Chi-San
Ai Chai-Sam, Ai Chih-San, Shorty San, Ngai Chi-Sam

Filmography (1966-1997)

Actor (22 films)
Flamenco Star (1966)
Si Guang Biao (1966)
Silly Brother (1966)
The Bamboo Grows Smooth (1967)
Stupid Bride Han Zi-Xu (1967)
Wandering Four Brothers and Sisters (1968)
Unforgettable Heartless Person (1968)
People's Fate (1968)
Draw Tiger, Draw Orchid (1968)
Madam Is Not at Home (1969)
More People More Luck (1969)
Women Shrine (1969)
Ah Hua Sheng Bao Zi (1969)
Qing Nan Shou (1969)
Brother Ah San Enters Town (1969)
The Ferocious Brothers (1972)
Chinese (1972)
The Righteous Fist (1972) ... Yang servant / Stutterer
Rikisha Kuri (1973)
Shaolin Kung Fu (1974)
Little Killer (1974)
Yan Gui Zai Ni Zuo You (1997)

and

侯元三
Hou Yuan-San

Filmography (1969-1974)

Actor (4 films)
Fixed Prize (1969)
Arrogant Uncle Ah Hsi (1969)
The Killer Must Pay (1973)
Shaolin Kung Fu (1974)

and

侯小三 ♂
Hou Hsia-San
Hau Siu-San, Hou Hsiao-San

Filmography (1969-1975)

Actor (6 films)
Bloody Mask (1969)
The Young Avengeress (1969) ... Greedy servant
Clam Fairy (1970)
Golden Sword and the Blind Swordswoman (1970)
Queen of Fist (1973)
When Hell Broke Loose (1975)

Result:

https://hkmdb.com/db/people/view.mhtml? ... ay_set=eng